1. Field of the Invention
Relates to rotary type engines and particularly to vane type rotary engines. Relates more particularly to vane type rotary engines of composite structure employing an Otto cycle and Stirling cycle on one shaft.
2. Description of the Prior Art
In any internal engine there presently exists the problem of disposing of undesirable exhaust emissions. In a single cycle Otto engine burning gasoline, as is most common today, there does not presently exist a design which reduces both the NO.sub.2 + N.sub.O and unburned hydrocarbons. General practice is to design the engine for a particular purpose and then remove resultant emissions through the addition of power consuming add-on devices such as thermactors, afterburners, and catalytic chambers.
The combining of the Otto cycle with the Stirling cycle is itself not new as shown by the U.S. Pat. No. 3,180,078 to Liston (copy enclosed herewith). As Liston observed, however, at lines 3 through 8 of page 1, "In an internal-combustion engine operating under varying speeds and loads, wide variations occur in the temperature of the exhaust gases; and when the exhaust gases are used to heat the hot space of a Stirling engine, the output of the latter engine will vary with the temperature of the exhaust gases". This is particularly true in a piston engine as employed by Liston or even the present Wankel type rotary engines due to the pulsating exhaust. Liston recognized the potential of the unburned hydrocarbons for producing additional heat but was required to go to a mechanized flip-flop system of selectively burning or non-burning of the unburned hydrocarbons as sensed by additional instrumentation.
In addition to the exhaust of the piston engine being pulsed, thus alternating high temperature inputs with cooling intervals, the Liston engine Stirling element overlaps cycle functions and reverses gas flows. This overlap is inherent in the piston design indicated and is described at lines 57-69 of page 2 of Liston's patent.
The basic device employed in the present invention being a plurality of vanes moving between sinusoidal covers is also not a new concept in itself as shown by the U.S. Pat. No. 3,762,844 to Isaksen and the Swiss Pat. No. 388,781 to Keller (copies enclosed herewith). The embodiment as shown is, however, novel in many of its features particularly as adapted to the specific application as will hereinafter be described.
In Isaksen's engine and Keller's embodiment of FIG. 4, a generally triangular vane is pivoted on a pin at the hub near the rotating shaft. This approach creates two problems. First, the centrifugal forces in the rotating vanes are borne by the pivot pins and the thin webs of the vanes adjacent to the pivot pin holes in the vanes. This, of course, creates a fatigue and possible failure point. Moreover, the pivot pin must be removed to remove a vane for servicing. Second, and most important, as the pivot pins and vanes wear, the vanes tend to move away from the confining surfaces thus creating a loss of the compression seal. A similar wear problem is created in the main embodiments of Keller as shown in FIGS. 1 through 3.
Thus, it is the prime objective of the present invention to provide a composite cycle engine which does not reverse flow direction in the Stirling cycle and, more importantly, does not overlap cycle functions. Said engine's Stirling cycle to compress the working gas to minimum volume before it is heated and to expand the working gas to maximum volume before cooling.
It is another object of the present invention to provide a composite cycle engine wherein the Otto cycle portion not only provides higher energy exhaust, but wherein said engine is able to convert more of that available heat energy to mechanical work in its Stirling cycle.
It is yet a further object of the present invention to provide a composite cycle engine of compact design and light weight.
It is still another object of the present invention to provide a composite cycle engine of the moving vane type wherein the vanes do not lose compression upon wear and being of a design maximizing ease of maintenance and repair while minimizing failure rate.